This invention relates in general to electrical connectors. More specifically, it relates to an upper surface connector for armored cables used in oil wells where the connector has a quick disconnect electrical relay circuit that shuts off the main power flow through the connector before arcing can occur.
Electrical connectors for armored cables are particularly important in the production of oil. Submersible pumps are often used in an oil well to extract the maximum volume of oil from the well site. Such pumps rest in the oil at the bottom of the well. Armored cables conduct electrical power from ground level to the pump. A typical cable has multiple power conductors, each with their own insulation, surrounded by further insulation and an outer metallic jacket. The conductors are capable of carrying current at high power levels, for example, 100 amperes, at high voltages, for example, 3,000 volts RMS. The armor jacket and heavy insulation are necessary to protect the conductors from both mechanical damage and the corrosive or explosive capabilities of fluids in the well such as liquid oil or water and flammable hydrocarbon gases that are often under very high pressures--several thousand pounds per square inch (psi). At "upper" or surface connectors mounted at the exterior of the wellhead in a normal atmosphere, combustion problems are enhanced by the presence of oxygen gas. Heretofore no "upper" electrical connector has been rated as "explosion proof." A principal problem has been the leakage of gas past couplings between the connector and an adjoining element (e.g. the socket of a feed-through mandrel for a wellhead or packer). This leakage problem has been particularly evident under dynamic conditions, where there are rapid changes in pressure or temperature, and where there is an aging of resilient materials that form a seal against the fluids.
The present invention is an improvement on the connector described in U.S. Pat. No. 3,945,700 which is commonly assigned with the present application. The '700 connector has as its principal components (1) a generally cylindrical housing that receives an armored cable at one end, (2) internal mold rubber bodies that guide and seal the conductors of the cable and their immediately surrounding insulation, (3) "contactor tubes" mounted in one of the rubber bodies which are electrically connected to a conductor and form a socket, and (4) a rotating, threaded coupling system that replaceably secures the connector to a mating cylindrical "socket" with pin contacts that are received in the contactor tubes. The coupling system includes a coupling sleeve and a coupling ring rotatably mounted on the sleeve. One end of the sleeve is seated in an annular groove formed in the main rubber body. The other end, which carries the coupling ring, is external to the rubber body and the housing. The coupling ring is also at the exterior of the connector where it is directly exposed to the fluid environment.
The '700 connector has proven to be reliably explosion resistant when used as a lower connector (at the interior of the wellhead or packer secured to a socket mounted at the bottom of a wellhead or packer feed-through mandrel), however, this connector has not been rated as explosion proof when adapted for use as an upper connector. A principal reason is the fluid leakage problems noted above. Rapid pressure and temperature variations will allow fluids to leak "under" the coupling ring where they can seep further inside the connector. Material fatigue over time, particularly of thin-walled rubber parts, can result in deformation or movement of components that will allow fluid leakage. Leakage is also possible if the coupling ring becomes loose or is purposely loosened for adjustment. If the fluid is a combustible gas, then there is an increased danger of an explosion at the connector. Other fluids can cause corrosion and a deterioration of the performance of the connector over time.
Another problem is that if the power is accidentally left on during the uncoupling of a connector, then there will be arcing between the electrical connectors as they disengage. If combustible fluids are present, as is often the case, this arcing can lead to an explosion. This problem is particularly significant at upper surface connectors where oxygen gas is present.
It is therefore a principal object of this invention to provide an electrical connector system for an upper surface connector with an electrical disconnect system that cuts off power through the main power conductors before they arc as their contacts break electrical connection.
Another object of this invention is to provide a connector system that is extremely explosion proof even at an upper connector of a wellhead located in an atmosphere containing oxygen gas and even if the electrical power is accidentally left on during an uncoupling of the connector.
A further object is to provide a connector system that blocks the flow of fluids, including gases under high pressure, to the interior of the connector even where the connector is subjected to rapid variations in temperature or pressure or where the connector is more prone to leak fluids due to material fatigue and general aging.
Another object is to isolate the interior of the connector system from hostile or combustible fluids until the quick disconnect system shuts off electrical power in the main conductors.
A still further object is to provide an improved connector with the foregoing advantages with only few modifications to known, commercially successful connectors.